The function of root canal fillings is to completely seal the prepared root canal to prevent infection of the surrounding tissue and possible failure of the root canal. The goal is to obtain as tight a seal as possible and to block off all openings through which infection could occur. The better the seal, the better the prognosis for the root canal.
Root canal sealers or cements are used in conjunction with gutta percha solid cores to achieve the best seal possible of the root canal. The root canal sealer is inserted into the canal first and the gutta percha cone is used to force the root canal sealer into the space between the root canal wall and the gutta percha and effectively fill canal irregularities.
However, as there is no adhesion between the root canal sealer and the gutta percha cone and the adhesion between the root canal sealer and root canal wall is incomplete, percolation of tissue fluids, saliva and bacteria in this space is possible. This percolation of fluids and bacteria will likely lead to infection and subsequent failure of the root canal.
A majority of the root canal sealers available today use zinc oxide as the main ingredient with varying degrees of different components to make up the powder. This powder is mixed with a liquid, usually eugenol, until a creamy mixture results. This mixture is then inserted into the root canal,
The problem appears to be with the zinc oxide component. It is inflammatory and cytotoxic to the surrounding tissue. This causes pain, bacterial attraction, and delayed healing. Therefore, lowering the zinc oxide content of the root canal sealer would alleviate some of the cytotoxic and inflammatory effects.
Several root canal sealers having a variety of zinc oxide based formulations have been used in the past. However, many of these sealers set quickly and provide inadequate working time for the dentist. Some sealers have high levels of zinc oxide causing severe inflammation in the surrounding tissue. Others do not flow well into canal irregularities.
With most root canal sealers, inflammatory reactions also occur due to spaces within the canal that are created as the root canal sealer is resorbed and dissolved in tissue fluid. Thus if the sealer is not sufficiently antimicrobial, when the sealer material disintegrates and the particles are removed from the canal by phagocytes, voids are left. These voids provide places for infection and inflammation to occur, which leads to eventual failure of the root canal. It may take anywhere from 6 months to 2 years for the failure to occur. The presence of an antimicrobial component could prevent this failure.
An ideal root canal sealer would exhibit the following characteristics: antimicrobial capacity; relatively non-irritating and non-inflammatory; adequate working time before setting; effectively seal both the apical and coronal ends of the root canal; and flow into canal irregularities.
Therefore, there is a need for a less-inflammatory root canal sealer that has a high level of antimicrobial effect in the canal with an adequate working time for the dentist.